This invention relates generally to an apparatus for supplying fuel to a liquefied petroleum gas (LPG) engines and more particularly to an automatic regulating apparatus of fuel supply to a carburetor of the engine in accordance with the composition of the LPG with the temperature of air to be mixed with the fuel.
The liquefied petroleum gas which may be prepared by compressing propane, butane or a mixture thereof is generally used as fuel of the internal combustion engine. The relation between an atmospheric temperature and a vapor pressure of the LPG fuel is kept constant in accordance with the composition of the fuel or the proportion of propane and butane.
It is preferable to control a mixture ratio of fuel gas and air to be supplied to the internal combustion engine to a theoretical mixture ratio, that is, an excess air ratio of 1 when the fuel is supplied to the engine. Since, however, the change of the composition ratio of the fuel gas effects to the specific gravity of the fuel, it is necessary to adjust the mixture ratio depending upon the composition of the fuel.
To this end, Japanese Utility Model Application No. 116,533 of 1973 (Provisional Utility Model Publication No. 60424 of 1975) discloses an apparatus for regulating the fuel supply to a LPG engine in which the temperature and the vapor pressure of the LPG to be supplied to the engine are detected and analyzed to confirm the composition of the fuel, and electric signals which correspond to the composition of the fuel confirmed are used for adjusting the fuel flow to the engine. There are, however, disadvantages that the above prior art apparatus requires to provide electrical operation units for detecting and analyzing the composition of the LPG, and the apparatus becomes more complicated in construction which is an extremely expensive in manufacture.
Furthermore, Japanese Patent Application No. 112,407 of 1973 (Provisional Patent Publication No. 63323 of 1975) teaches that an apparatus for controlling fuel supply to a liquefied petroleum gas to an internal combustion engine in which an amount of fuel to be supplied to the engine is adjusted mechanically in making use of the change of a vapour pressure of the fuel depending on the composition of the fuel. In this prior application, however, the ratio of the mixture of the fuel and air only is controlled with respect to the change of the composition of the fuel, but no consideration is taken in the change of the rate of the mixture with respect to the change of temperature being sucked into the engine, that is, the change of the ratio of the mixture of the fuel and air with respect to the change of the specific gravity of air.
In view of the above, it is a principal object of the present invention to provide an apparatus for regulating an amount of a gaseous fuel to be supplied to a liquefied petroleum gas engine in accordance with the composition of the fuel.
It is another object of the present invention to provide an apparatus for regulating fuel supply to LPG engine in sensing and detecting the temperature and pressure of a gaseous fuel being supplied to the engine.
It is still another object of the present invention to provide the above mentioned apparatus which is simple in construction, reliable in use and low in cost.